Just checking the WotC catalog i could confirm the release date of the Dark Sun product line to be on August 17th of 2010.
http://www.wizards.com/dnd/Catalog.aspx?sort=date-desc&page=0
The books will be a little diferent from the Eberron and FR, the DS will get:
- Campaing Setting (will have info for both DM and Players)
- Marauders of the Dune Sea - Adventure (2nd to 5th level starting right at the end of the novel "Verdant Passage)
- Creature Catalog (will use the former CS cover, and will feature monsters, hazards and so on)